Cleaning up PoP

As package on package technology moves deeper into the mainstream electronics, issues like cleaning are getting much more attention. PoP’s impressive growth, driven in large part by high volume portables like cameras and cell phones, requires fine densities that make it difficult to remove residues after soldering.

Zestron America recently did some studies of cleaning processes, comparing various processes to determine the best results. No-clean fluxes are often recommended, but cleaning is often needed to improve reliability. Cleaning is difficult since the spacings on PoP are very tight.

“On the top level, we had a 0.65 mm ball pitch. On the bottom level, we tested a 0.5 mm ball pitch,” said Umut Tosun, application technology manager at Zestron America. He detailed his test during the most recent offering in the IPC Spring Webinar series.

The study began with the production of 14 mm boards. They were run through soldering processes at various conveyor speeds in different environments, such as with high nitrogen content. Multiple cleaning agents were also used.